Radio receiving apparatus



June 22 1926. 1,589,925

R. R. BATCHER RADIO RECEIVING APPARATUS Filed Dec. 19, 1924 2N0 DETECTIFA SOOOON AMPLIFIER Patented June 22,1926.

UNITED STATES PATENT OFFICE.

mm REYNOLDS BATCHEB, OI JAIAICA, NEW YORK, ASSIGNOB TO A. H. GREBE 8c(X7 110., RICKIOND HILL, NEW YORK, A CORPORATION OF NEW YORK.

mm nncmvme Arrm'rus.

Application Med December 19, 1924. Serial in, 756,958.

The present invention is particularly adapted for use in connection withthe socalled super-heterodyne receiving system, in

which an intermediate frequency amplifier is fed from the beats producedwhen the 0S1 cillations of a local oscillator are imposed upon theoscillations set up in the receiving system by the received signal; thelocal oscillator being adjusted to a frequency difiering from thefrequency of the recelved signal, the difference being equivalent to theresonant frequency of the intermediate amplifier. Two controls arenecessary for the operation of the super-heterodyne receivers 5 now ingeneral use. It is my purpose to.

show how these two adjustments can be made with one dial or controlhandle.

The difliculty encountered when attempting to mechanically interlockthese two controls is that the proper frequency relation cannot bemaintained for more than one station, because the frequency increment isgreater per division on one dial control than on the other.

Simply stated, the present invention con sists of so designing thecircuits, more par 'ticularly the variable condensers in the circuits,that a constant frequency increment is produced for a correspondingmovement of the control dial, thus permitting the vari-- quency of thedesired signal. With the im-- proved system described here, not only theadvanta resulting when the same station is found at several settings, isavoided by using the" constant frequency system, which requires onlyonecontrol knob.

It should be understood that the use of strai ht line frequencycondensers has been mentioned in the foregoing only because of the factthat the resultant equal spacing of stations'along the. dial scale ofthis type of condenser is a decided advantage in considering the plannow in force in connection I with broadcast transmitting stations, whichthermore with the straight line the oscillator adjusted to a freofsingle control is obtained, but in addition the confusion to theoperator,-

provides for a separation of stations intermsof frequency rather thanwave-len th; furf requency condenser the same ease ofstuning stations isafforded on the lower dial scale as on the upper dial scale. Theinvention is based upon the proposition of maintaining a constantfrequency relation between circuits. The figure is a circuit diagram inwhich the rotors of the tuning condenser C and C are mechanically andincidentally electrical-. ly connected, the shaft serving as the commonmechanical connection, terminating in a-control knob dial D. The circuitconsisting of a loop L, the primary of a coupling- 70 transformer L, thegrid biasing battery N and the variable tuning condenser C is connectedto the grid and filament of the vacuum tube VT. The variable condenser Cis so designed that the circuit willrespond to a fre uency of from 1500to 500 kiloc cles w en the control knob is moved t rough its completerange of 180 degrees. The plate circuit of the vacuum tube VT includesan inductance L and a capacity C. the values of which are such'as torespond to a frequency of kilocycles. The oscillator circuit consists ofthe inductance L and one side L of the coupling transformer K shunted bythe variable condenser C 35 It should be understood that thesedesignated frequencies have been chosen merely for the purpose ofexplanation and that a receiving set of the super-heterodyne type may bemade to function with quite a number of'other frequency differences,rovided particularly that the frequency 0 the in-v termediate amplifierdoes not come within the limits of audibility. Thus, 100 kilocyclesdifference might --'ust as well be used provided the interme iateamplifier has been adjusted to 0 rate o this same frequency.

The gri and filamentof the vacuum tube VT are included in this circuitand in addition an inductance L! is included in the plate circuit of thevacuum tube and is placed in inductive relation with the inductance Ifor the purpose of sustaining oscillations. The variable condenserC isso; designed as to cause a circuit which includes the cou- 1 plinginductance L to vary the frequency of the oscillations from 1550 to 550when the control dial D is rotated through its 180 degree range.- Theconstant f uency increment characteristic of both variable con- Theintermediate frequency amplifier (50.

kilocycles, amplifier IFA) 1s shown connected to the tuned plate circuitLand C of the vacuum tube VT the output of the intermediate amplifierIFA is shown connected-to the detector and audio amplifier DA, theoutput ofthe latter being connected to a loud speaker. I While theadvantages of equal "spacing of stations over the dial range may not beob- 'tained with condensers of different characteristics, the constantfrequency relation system may be operated where thecondenser C is anordinary semi-circular plate variable condenser, provided the variablecondenser C is designed in suchv a manner as to rovvide for a constantfrequency when boti C and C are mechanically locked to the same shaftand rotated together forthe purpose oftuning, furthermore, two moresemi-circular plate variable condensers which are not mechanicallylocked together may. be

operated from a sin le dial, provided a cam or other mechanica systemfor imparting mechanical motion with varying increment is used.

Having thus described my invention, what I claim is: v

1., A signal receiving system comprising said tuning means so as tomaintain constant variable tuning condensers a apted to give an inputcircuit and an oscillator circuit, each of said circuits being providedwith requisite tuning means including variable elements adapted to givea straightline'fre- .quency variation, and said circuits being tuned-todifferent predetermined frequencies, and means for simultaneouslyvarying the said frequenc difference.

' 2. A signa receiving system comprising an input circuit and anoscillator circuit, each of said circuits being rovided with a straightline frequency variation, said tuning condensers being relatively soadjusted as to give said circuits a predetermined frequency difl'erence,and means to 'maintain constant throu hout the operating range saidfrequency di erence.

3. A signal receiving system comprising an input circuit and an"oscillator circuit, each of said circuits being provided with variabletuning means adapted to give a straight line frequency variation, thesaid tuning means being mechanically connected in fixed relation andrelatively adjusted to -mainta'in a predetermined frequency differencebetween said circuits, and a tuning control common to the said tuningmeans.- I

4. A signal receiving system comprising an input circuit and anoscillator circuit, each of said circuits being provided with variabletuning means adapted to give a straight line freqlllenc variation, thevari-- able elements of t c said tuning means being mounted upon acommon shaft and fixed thereon in such angular relation as to maintain apredetermined frequency difference between said circuits.

' RALPH REYNOLDS BATGHER.

